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Dapol 7mm Class 08 Shunter BRC Conversion
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 Posted: Wed Jan 4th, 2017 02:57 pm
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I've started to install battery radio control into my Dapol 0-gauge shunter using a Deltang Rx61b Rx.

I chose this Rx simply because it was being sold cheap (Rx 61d is the current version as I type) and it's 1.3A max motor output is more than enough for this little gem of a loco, which draws about 0.12A trundling along at medium speed, and around 0.28A at 12v with 100% wheelslip. 

I don't bother worrying about stall current any more...in 40 years of model railways I've only had one loco stall solid, which was when as a truculent teenager, I jammed the pencil into the running gear of a passing Triang Britannia. This 'rule' was made up when Decoders/Rx cost the amount of a week's food shop (whereas now they cost an extra large pizza with 4 toppings) and is in dire need of revising IMHO. That being said...I've added some heatsink to the Rx because I happen to have the room...and am a firm believer in sod's law. ;)

I want to leave the existing electronics un-hacked so have started by building an interface to the 21pin DCC/MTC header.




I have popped some jumper wires with coloured female header connectors on for show at this stage. I don't know if there will be room to use these but it would be nice to be able to unplug individual components if need be...we shall see. The pins that will be in use (apart from track pickups, top-right, which I bent by mistake) have been bent at 90 degrees, otherwise the connectors will hit the roof.  You'll notice I've used the relevant DCC-standard colours! :cool:

I need to double-check the track pickups only go to the header pins and are not used for any DC chicanery on the PCB...I want to leave in place if at all possible to preserve as much "back-to-factory(or DCC)-ness" as possible.  Their touch is incredibly light so I wouldn't expect it to make a perceptible difference to battery life.  I am also toying with the concept of track-powered re-charging...but that is a couple of years and house-move away at least!



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 Posted: Wed Jan 4th, 2017 03:16 pm
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Not sure at this stage what lights I want lit up with what functions...so I can easily fiddle about later I tracked what LED was wired where on the three plug/sockets.




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 Posted: Wed Jan 4th, 2017 06:56 pm
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" I jammed the pencil into the running gear of a passing Triang Britannia."

Arh ... The good ol' days !

I remember my Tri-ang 'Dock Authority' cornering at 45deg, like it was yesterday. ;)


Nice work Fil.

You could seriously eat for a LONG TIME for the price of an RC receiver. :f:


:moose:

Si.



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 Posted: Wed Jan 4th, 2017 11:13 pm
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Si. wrote: " I jammed the pencil into the running gear of a passing Triang Britannia."

Arh ... The good ol' days !

I remember my Tri-ang 'Dock Authority' cornering at 45deg, like it was yesterday. ;)


Nice work Fil.

You could seriously eat for a LONG TIME for the price of an RC receiver. :f:


:moose:

Si.


Thanks Si, yes I used to use Antenna models ESC and separate Rx in sunset brass 0-scale a while back....16-wheel bogie tenders packed with NiCd! :bg:  Then I went G for a bit. Now I'm in a flat but saving for the day when I can get back out in a garden again. In the meantime...this stuff is for my "bottom drawer" ;)



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 Posted: Wed Jan 4th, 2017 11:29 pm
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Let's put the charging/status LEDs where they can be seen!



Not wired up here just shining light through the back of them.





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 Posted: Wed Jan 4th, 2017 11:46 pm
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Hmm. At this stage I was beginning to regret this idea! Should look for some finer wire really, at least for the LEDs. Some of the others carry battery voltage/charging currents however so can't really skimp there.

Where to put the charging socket though? Don't want to have to tip the loco over or keep taking the PCB/socket access cover off as I don't want that becoming a loose fit... L:





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 Posted: Thu Jan 5th, 2017 12:04 am
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Open the door...




...to reveal a micro USB charging socket. Yes the idea here is to charge the single LiPo with any old USB phone charger. :2t:

A voltage booster will be used to lift the voltage for a sensible top speed...more on that later...a lot later :shocked:



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 Posted: Thu Jan 5th, 2017 11:37 pm
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My cutting mat is handily printed with 10mm squares for scale.

So on the right is the actual charging module that takes care of the battery while charging. Because I didn't want this relatively large module in the cab I extended the input socket to the significantly smaller micro USB header PCB as shown on the left.


I also have to remove the surface mount LEDs on the charging module (they are the tiny oblongs top-centre) and wire from their previous contact points to the LEDs I mounted in the cab instrument panel. Time for some serious squinting! :shocked:






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 Posted: Thu Jan 5th, 2017 11:48 pm
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So after much holding of breath here is the charging module, with leads soldered on for the shunter's LED instrument panel, a JST male connection for the battery, and the input wires that come from the USB socket in the cab.

I will check all the lights light up as they should and then hot-glue the wires in place to stop any movement that would stress the soldered joints as I move the module about.




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 Posted: Fri Jan 6th, 2017 12:41 am
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Another needless requirement I wrote into the spec of this project was to make the power switch invisible yet accessible without having to lift or otherwise manhandle the loco. I thought briefly about read switches but didn't want magnets or the, albeit miniscule, battery drain of latched relays. (I also for a few seconds had the crazy idea of using a switch behind one of the sprung buffer shafts until I realised the loco would turn itself off in the process of its duties! :Crazy:)


So after much head-scratching L: I hit upon this idea. 

See if you can guess where I put the switch from the video... :bg:





The back of the door is reinforced with some 2mm plastikard which makes it feel a lot more solid and positive.



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